1. Field of the Invention
The present invention relates to a spin-valve thin film magnetic element in which electric resistance is changed with the relation between the direction of pinned magnetization of a pinned magnetic layer and the magnetization direction of a free magnetic layer influenced by an external magnetic field. Particularly, the present invention relates to a spin-valve thin film magnetic element having excellent heat resistance, a thin film magnetic head comprising the spin-valve thin film magnetic element, and a method of manufacturing the spin-valve thin film magnetic element which is capable of easily crossing at right angles the magnetization direction of a free magnetic layer and the magnetization direction of a pinned magnetic layer.
2. Description of the Related Art
Magnetoresistive heads include an AMR (anisotropic magnetoresistive) head comprising an element exhibiting a magnetoresistive effect, and a GMR (giant magnetoresistive) head comprising an element exhibiting a giant magnetoresistive effect. The AMR head comprises an element exhibiting the magnetoresistive effect and having a single layer structure comprising a magnetic material. On the other hand, the GMR head comprises an element having a multilayer structure comprising a lamination of a plurality of materials. Although there are some types of structures that create the giant magnetoresistive effect, a spin-valve thin film magnetic element has a relatively simple structure and exhibits a high rate of change in resistance with a weak external magnetic field.
FIGS. 12 and 13 are sectional views respectively showing the structures of examples of conventional spin-valve thin film magnetic elements, as viewed from the surface side facing a recording medium.
In each of the examples, shield layers are formed above and below the spin-valve thin film magnetic element with gap layers provided therebetween. Namely, a reproducing GMR head comprises the spin-valve thin film element, the gap layers, and the shield layers. A recording inductive head may be mounted on the reproducing GMR head.
The GMR head is provided at the trailing side end of a floating slider together with the inductive head to form a thin film magnetic head, for detecting a recording magnetic field of a magnetic recording medium such as a hard disk or the like.
In FIGS. 12 and 13, the movement direction of the magnetic recording medium coincides with the Z direction shown in the drawings, and the direction of a leakage, magnetic field from the magnetic recording medium coincides with the Y direction.
The spin-valve thin film magnetic element shown in FIG. 12 is a so-called bottom type single spin-valve thin film magnetic element comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer.
The spin-valve thin film magnetic element shown in FIG. 12 comprises a multilayer film 33 comprising a base layer 31, an antiferromagnetic layer 22, a pinned magnetic layer 23, a nonmagnetic conductive layer 24, a free magnetic layer 25 and a protecting layer 32, a pair of hard bias layers (permanent magnet layers) 29 formed on both sides of the multilayer film 33, and a pair of electrode layers 28 respectively formed on the hard bias layers 29.
Each of the base layer 31 and the protecting layer 32 comprises a Ta film or the like. The track width Tw is determined by the width dimension of the upper side of the multilayer film 33.
In general, the antiferromagnetic layer 22 comprises a Fexe2x80x94Mn alloy film or a Nixe2x80x94Mn alloy film, each of the pinned magnetic layer 23 and the free magnetic layer 25 comprises a Nixe2x80x94Fe alloy film, the nonmagnetic conductive layer 24 comprises a Cu film, each of the hard bias layers 29 comprises a Coxe2x80x94Pt alloy film, and each of the electrode layers 28 comprises a Cr film, or a W film.
As shown in FIG. 12, magnetization of the pinned magnetic layer 23 is put into a single magnetic domain state in the Y direction (the direction of a leakage magnetic field from the recording medium: the height direction) due to an exchange anisotropic magnetic field with the antiferromagnetic layer 22, and magnetization of the free magnetic layer 25 is oriented in the direction opposite to the X1 direction due to the influence of a bias magnetic field from the hard bias layers 29.
Namely, the magnetization directions of the pinned magnetic layer 23 and the free magnetic layer 25 are set to cross at right angles.
In the spin-valve thin film magnetic element, a sensing current is supplied to the pinned magnetic layer 23, the nonmagnetic conductive layer 24 and the free magnetic layer 25 from the electrode layers 28 formed on the hard bias layers 29. The movement direction of the recording medium such as a hard disk or the like coincides with the Z direction. When a leakage magnetic field is applied from the recording medium in the Y direction, the magnetization direction of the free magnetic layer 25 is changed from the direction opposite to the X1 direction to the Y direction. In the free magnetic layer 25, the electric resistance is changed (referred to as a magnetoresistive effect) with the relation between the change in the magnetization direction and the pinned magnetization direction of the pinned magnetic layer 23 so that the leakage magnetic field from the recording medium is detected by a change in voltage based on the change in electric resistance.
The spin-valve thin film magnetic element shown in FIG. 13 is a so-called bottom type single spin-valve thin film magnetic element comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer.
In FIG. 13, reference character K denotes a substrate on which an antiferromagnetic layer 22 is formed. Furthermore, a pinned magnetic layer 23 is formed on the antiferromagnetic layer 22, a nonmagnetic conductive layer 24 is formed on the pinned magnetic layer 23, and a free magnetic layer 25 is formed on the nonmagnetic conductive layer 24.
Furthermore, bias layers 26 are formed on the free magnetic layer 25 with a space equal to the track width Tw therebetween, and conductive layers 28 are respectively provided on the bias layers 26.
The pinned magnetic layer 23 comprises, for example, a Co film, a NiFe alloy film, a CoNiFe alloy film, a CoFe alloy film, or the like.
The antiferromagnetic layer 22 is composed of NiMn.
Each of the bias layers 16 comprises an antiferromagnetic material such as a FeMn alloy having a face-centered cubic disordered crystal structure.
The pinned magnetic layer 23 shown in FIG. 13 is magnetized by an exchange anisotropic magnetic field produced in the interface with the antiferromagnetic layer 22 due to exchange coupling. The magnetization direction of the pinned magnetic layer 23 is pinned in the Y direction shown in the drawing, i.e., the direction away from the recording medium (the height direction).
The free magnetic layer 25 is magnetized by an exchange anisotropic magnetic field of the bias layers 26 to be put into a single magnetic domain state. The magnetization direction of the free magnetic layer 25 is oriented in the direction opposite to the X1 direction shown in the drawing, i.e., the direction crossing the magnetization direction of the pinned magnetic layer 23.
The free magnetic layer 25 is put into the single magnetic domain state by the exchange anisotropic magnetic field of the bias layers 26, thereby preventing the occurrence of Barkhausen noise.
In the spin-valve thin film magnetic element, when a stationary current is supplied to the free magnetic layer 25, the nonmagnetic conductive layer 24 and the pinned magnetic layer 23 from the conductive layers 28 to apply, in the Y direction shown in the drawing, a leakage magnetic field from the magnetic recording medium moved in the Z direction, the magnetization direction of the free magnetic layer 25 is changed from the direction opposite to the X1 direction to the Y direction. In the free magnetic layer 25, the electric resistance is changed with the relation between the change in the magnetization direction and the magnetization direction of the pinned magnetic layer 23 so that the leakage magnetic field from the recording medium is detected by a change in voltage based on the change in electric resistance.
In the spin-valve thin film magnetic element shown in FIG. 13, as shown in FIG. 14, the layers ranging from the antiferromagnetic layer 22 to the free magnetic layer 25 are formed, and then heat-treated (annealed) in a magnetic field to cause an exchange anisotropic magnetic field in the interface between the pinned magnetic layer 23 and the antiferromagnetic layer 22 so that the magnetization direction of the pinned magnetic layer 23 is pinned in the Y direction shown in the drawing. Then, as shown in FIG. 15, a lift off resist 351 having a width corresponding to the track width is formed. Then, the bias layers 26 and the conductive layers 28 are formed on the portions of the surface of the free magnetic layer 25, which are not covered with the lift off resist 351. After the lift off resist 351 is removed, the magnetization direction of the free magnetic layer 25 is oriented in the direction of the track width to produce the spin-valve thin film magnetic element shown in FIG. 13.
However, the conventional spin-valve thin film magnetic element shown in FIG. 12 has the following problems.
Although magnetization of the pinned magnetic layer 23 is magnetized in the Y direction to be brought into the single magnetic domain state, the hard bias layers 29 magnetized in the direction opposite to the X1 direction are provided on both sides of the pinned magnetic layer 23, and thus, particularly, the magnetization directions on both sides of the pinned magnetic layer 23 are not pinned in the Y direction due to the influence of the biased magnetic field from the hard bias layers 29.
Namely, the magnetization direction of the free magnetic layer 25, which is put into the single magnetic domain state in the direction opposite to the X1 direction by magnetization of the hard bias layers 29 in the direction opposite to the X1 direction, is not perpendicular to the magnetization direction of the pinned magnetic layer 23, particularly, near the side ends of the multilayer film 33. A reason for crossing the magnetization directions of the free magnetic layer 25 and the pinned magnetic layer 23 at right angles is that magnetization of the free magnetic layer 25 can be easily changed even by a small external magnetic field to greatly change the electric resistance, thereby improving reproduction sensitivity. Another reason is that an output waveform having good symmetry can be obtained.
Furthermore, since magnetization in the vicinities of the side ends of the free magnetic layer 25 is easily pinned by the influence of strong magnetization of the hard bias layers 29, the magnetization is less changed by an external magnetic field. Therefore, dead regions with low reproduction sensitivity are formed near the side ends of the multilayer film 33, as shown in FIG. 12.
In the multilayer film 33, the central region except the dead regions is a sensitive region which substantially contributes to reproduction from the recording medium and which exhibits the magnetoresistive effect. The width of the sensitive region is shorter than the track width Tw, which is set in forming the multilayer film 33, by a length corresponding to the width dimensions of the dead regions, and the track width Tw cannot be precisely defined due to variations in the dead regions. There is thus the problem of causing difficulties in complying with an increase in recording density by narrowing the track width Tw.
In the spin-valve thin film magnetic element shown in FIG. 13, the magnetization direction of the free magnetic layer 25 is oriented in the direction crossing the magnetization direction of the pinned magnetic layer 23 by an exchange bias system using the bias layers 26 comprising an antiferromagnetic material.
The exchange bias system is a system suitable for high-density recording with the narrow track width Tw, as compared with a hard bias system, which is difficult to control the effective track width Tw due to the presence of the dead regions.
However, the spin-valve thin film magnetic element shown in FIG. 13 has a problem of corrosion resistance because the antiferromagnetic layer 22 comprises a Nixe2x80x94Mn alloy. A spin-valve thin film magnetic element comprising the antiferromagnetic layer 22 comprising a Nixe2x80x94Mn alloy or Fexe2x80x94Mn alloy also has a problem in which it is corroded with a weak alkali solution or an emulsifier containing sodium tripolyphosphate used in the process for manufacturing a thin film magnetic head to decrease the exchange anisotropic magnetic field.
Since the antiferromagnetic layer 22 comprises a Nixe2x80x94Mn alloy, the antiferromagnetic layer used for the bias layers 26 is limited, thereby causing the problem of deteriorating the heat resistance and corrosion resistance of the bias layers 26. Namely, in order to form the bias layers 26 having high heat resistance, it is necessary to select an antiferromagnetic material such as a Nixe2x80x94Mn alloy or the like which can produce an exchange anisotropic magnetic field in the direction opposite to the X1 direction in the interfaces between the bias layers 26 and the free magnetic layer 25 in heat treatment in a magnetic field in the direction crossing the exchange anisotropic magnetic field in the Y direction, which is produced in the interface between the antiferromagnetic layer 22 made of a Nixe2x80x94Mn alloy and the pinned magnetic layer 23.
However, in heat treatment in the magnetic field, the exchange anisotropic magnetic field acting in the interface between the antiferromagnetic layer 22 and the pinned magnetic layer 23 is inclined from the Y direction to the direction opposite to the X1 direction, and thus the magnetization direction of the pinned magnetic layer 23 is not perpendicular to the magnetization direction of the free magnetic layer 25. There is thus a problem in that a symmetric output signal waveform cannot be obtained.
Therefore, it is necessary to select an antiferromagnetic material which requires no heat treatment in a magnetic field, and which produces an exchange anisotropic magnetic field immediately after film deposition in the magnetic field.
For these reasons, the bias layers 26 are generally made of a FeMn alloy having a face-centered cubic disordered crystal structure.
However, in a magnetic recording apparatus, the temperature of the element is increased due to a temperature raise in the apparatus and Joule heat generated by the sensing current to decrease the exchange anisotropic magnetic field, thereby causing difficulties in bringing the free magnetic layer 25 in the single magnetic domain state. As a result, the problem of causing Barkhausen noise is brought about.
Furthermore, a Fexe2x80x94Mn alloy has lower corrosion resistance than a Nixe2x80x94Mn alloy, and thus has not only a problem in which it is corroded with a weak alkali solution or emulsifier containing sodium tripolyphosphate used in the process for manufacturing a thin film magnetic head to decrease the exchange anisotropic magnetic field, but also a problem in which corrosion proceeds in the magnetic recording apparatus to deteriorate durability.
The method of manufacturing the conventional spin-valve thin film magnetic element shown in FIGS. 14 to 16 comprises the step of forming the lift off resist 351 shown in FIG. 15 in which the surface of the uppermost layer formed between the substrate and the bias layers is exposed to air. Thus, the surface exposed to air must be cleaned by ion milling or reverse sputtering with a rare gas such as Ar or the like before an upper layer is formed. This cleaning increases the number of manufacturing steps. Furthermore, there are problems with cleaning by ion milling or reverse sputtering such as contamination with materials (which adhere to the surface), the adverse effect of a disordered surface crystal state on the occurrence of the exchange anisotropic magnetic field, and other difficulties.
In the method of manufacturing the conventional spin-valve thin film magnetic element, the track width Tw is defined by the bias layers 26 and the electrode layers 28 provided on both sides of the lift off resist 351, thereby causing variation in the track width Tw due to variation in the dimensions of the base end of the lift off resist 351.
The present invention has been achieved for solving the above-described problem, and an object of the present invention is to provide a spin-valve thin film magnetic element adaptable to high-density recording, in which the track width can be precisely defined by bias layers provided on flat portions of a free magnetic layer on both sides of a groove with no bias layer remaining in the groove in manufacturing the spin-valve thin film magnetic element.
Another object of the present invention is to provide a spin-valve thin film magnetic element in which materials of an antiferromagnetic layer and bias layers are improved to improve heat resistance.
A further object of the present invention is to provide a method of manufacturing the above-described spin-valve thin film magnetic element, in which the magnetization direction of a free magnetic layer and the magnetization direction of a pinned magnetic layer can easily be crossed at right angles.
A further object of the present invention is to provide a thin film magnetic head comprising the above-described spin-valve thin film magnetic element, having excellent durability and heat resistance, and producing a sufficient exchange anisotropic magnetic field.
In order to achieve the objects, the present invention comprises the following construction.
A spin-valve thin film magnetic element of the present invention comprises an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer so that the magnetization direction is pinned by an exchange anisotropic magnetic field with the antiferromagnetic layer, a nonmagnetic conductive layer formed between the pinned magnetic layer and a free magnetic layer, bias layers for orienting the magnetization direction of the free magnetic layer in the direction perpendicular to the magnetization direction of the pinned magnetic layer, and conductive layers for supplying a sensing current to the free magnetic layer, wherein the free magnetic layer comprises a track groove provided on the side opposite to the pinned magnetic layer side and having a width corresponding to the track width, and flat portions on both sides of the groove, and the bias layers are provided on the flat portions of the free magnetic layer.
While the arrangement of the layers has been described in a preferred embodiment, they may be operatively connected in other fashions as long as the required electrical, mechanical, and magnetic properties of a spin valve are achieved. They may have one or more additional layers between any or all of them.
In the spin-valve thin film magnetic element, since the free magnetic layer comprises the groove provided on the side opposite to the pinned magnetic layer side and having a width corresponding to the track width, the track width can be precisely determined according to the width of the groove.
In manufacturing the spin-valve thin film magnetic element, the bias layers provided on the flat portions of the free magnetic layer on both sides of the groove do not remain in the groove, and the magnetic moment of the free magnetic layer is smoothly rotated with a weak leakage magnetic field from a magnetic recording medium, thereby improving sensitivity.
Each of the antiferromagnetic layer and the bias layers is preferably composed of an alloy containing Mn, and at least one element of Pt, Pd, Rh, Ru, Ir, Os, Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr.
The spin-valve thin film magnetic element comprises the antiferromagnetic layer and the bias layers each composed of the above alloy, and thus exhibits good temperature characteristics of the exchange anisotropic magnetic field and excellent heat resistance.
The spin-valve thin film magnetic element also exhibits excellent durability when provided in a hard disk in which the element is heated to high temperature by the environmental temperature in the device, and Joule heat generated by a sensing current flowing in the element, and the exchange anisotropic magnetic field (exchange coupling magnetic field) less changes with a temperature change.
Furthermore, since the antiferromagnetic layer is made of the above alloy to increase the blocking temperature, a high exchange anisotropic magnetic field can be produced in the antiferromagnetic layer, and the magnetization direction of the pinned magnetic layer can be strongly pinned.
In the spin-valve thin film magnetic element, at least one of the pinned magnetic layer and the free magnetic layer may be divided into two parts with a nonmagnetic intermediate layer provided therebetween so that the divided magnetic layers are brought into a ferrimagnetic state in which the magnetization directions are 180xc2x0 different.
In the spin-valve thin film magnetic element in which at least the pinned magnetic layer is divided into two parts with the nonmagnetic intermediate layer provided therebetween, one of the two divided pinned magnetic layers functions to pin the other pinned magnetic layer in a proper direction, maintaining the pinned magnetic layers in a very stable state.
On the other hand, in the spin-valve thin film magnetic element in which at least the free magnetic layer is divided into two parts with the nonmagnetic intermediate layer provided therebetween, an exchange anisotropic magnetic field is produced between the two divided free magnetic layers to bring the free magnetic layers into a ferrimagnetic state, thereby permitting reversal with high sensitivity to an external magnetic field.
In the spin-valve thin film magnetic element, the antiferromagnetic layer is preferably made of an alloy represented by the following composition formula:
XmMn100xe2x88x92m
wherein X is at least one element of Pt. Pd, Rh, Ru, Ir, and Os, and the composition ratio m satisfies 48 atomic %xe2x89xa6mxe2x89xa660 atomic %.
The antiferromagnetic layer is preferably made of an alloy represented by the following composition formula:
XmMn100xe2x88x92m
wherein X is at least one element of Pt, Pd, Rh, Ru, Ir, and Os, and the composition ratio m satisfies 48 atomic %xe2x89xa6mxe2x89xa658 atomic %.
In the spin-valve thin film magnetic element, the bias layers are preferably made of an alloy represented by the following composition formula:
XmMn100xe2x88x92m
wherein X is at least one element of Pt, Pd, Rh, Ru, Ir, and Os, and the composition ratio m satisfies 52 atomic %xe2x89xa6mxe2x89xa660 atomic %.
In the spin-valve thin film magnetic element, the antiferromagnetic layer may be made of an alloy represented by the following composition formula:
PtmMn100xe2x88x92mxe2x88x92nZn
wherein Z is at least one element of Pd, Rh, Ru, Ir, and Os, and the composition ratios m and n satisfy 48 atomic %xe2x89xa6m+nxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
More preferably, the composition ratios m and n satisfy 48 atomic %xe2x89xa6m+nxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
In the spin-valve thin film magnetic element, the bias layers may be made of an alloy represented by the following composition formula:
PtmMn100xe2x88x92mxe2x88x92nZn
wherein Z is at least one element of Pd, Rh, Ru, Ir, and Os, and the composition ratios m and n satisfy 52 atomic %xe2x89xa6m+nxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
In the spin-valve thin film magnetic element, the antiferromagnetic layer may be made of an alloy represented by the following composition formula:
PtqMn100xe2x88x92qxe2x88x92jLj
wherein L is at least one element of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr, and the composition ratios q and j satisfy 48 atomic %xe2x89xa6q+jxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
More preferably, the composition ratios q and j satisfy 48 atomic %xe2x89xa6q+jxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
In the spin-valve thin film magnetic element, the bias layers may be made of an alloy represented by the following composition formula:
PtqMn100xe2x88x92qxe2x88x92jLj
wherein L is at least one element of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr, and the composition ratios q and j satisfy 52 atomic %xe2x89xa6q+jxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
Particularly, in the spin-valve thin film magnetic element comprising the antiferromagnetic layer and the bias layers having the same alloy composition, the following combinations 1 to 3 are preferred.
1. The antiferromagnetic layer and the bias layers preferably comprise an alloy having the following composition:
XmMn100xe2x88x92m
wherein X is at least one element of Pt, Pd, Rh, Ru, Ir, and Os, and the composition ratio m satisfies 52 atomic %xe2x89xa6mxe2x89xa658 atomic %.
The composition ratio m of the antiferromagnetic layer and the bias layers more preferably satisfies 52 atomic %xe2x89xa6mxe2x89xa656.5 atomic %.
2. The antiferromagnetic layer and the bias layers preferably comprise an alloy having the following composition:
PtqMn100xe2x88x92qxe2x88x92jLj
wherein L is at least one element of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr, and the composition ratios q and j satisfy 52 atomic %xe2x89xa6q+jxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
The composition ratios q and j of the antiferromagnetic layer and the bias layers more preferably satisfy 52 atomic %xe2x89xa6q+jxe2x89xa656.5 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
3. The antiferromagnetic layer and the bias layers preferably comprise an alloy having the following composition:
PtmMn100xe2x88x92mxe2x88x92nZn
wherein Z is at least one element of Pd, Rh, Ru, Ir, and Os, and the composition ratios m and n satisfy 52 atomic %xe2x89xa6m+nxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
The composition ratios m and n of the antiferromagnetic layer and the bias layers more preferably satisfy 52 atomic %xe2x89xa6m+nxe2x89xa656.5 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
Where the antiferromagnetic layer and the bias layers have different alloy compositions, the following combinations 4 to 6 are preferred.
4. The bias layers preferably comprise an alloy represented by the composition XmMn100xe2x88x92m wherein X is at least one element of Pt, Pd, Ir, Rh, Ru, and Os, and the composition ratio m satisfies 52 atomic %xe2x89xa6mxe2x89xa660 atomic %, and the antiferromagnetic layer preferably comprises an alloy represented by the composition XmMn100xe2x88x92m wherein X is at least one element of Pt, Pd, Ir, Rh, Ru, and Os, and the composition ratio m satisfies 48 atomic %xe2x89xa6mxe2x89xa658 atomic %.
The composition ratio m of the antiferromagnetic layer more preferably satisfies 52 atomic %xe2x89xa6mxe2x89xa655.2 atomic %, or 56.5 atomic %xe2x89xa6mxe2x89xa660 atomic %.
5. The bias layers preferably comprise an alloy represented by the composition PtqMn100xe2x88x92qxe2x88x92jLj wherein L is at least one element of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr, and the composition ratios q and j satisfy 52 atomic %xe2x89xa6q+jxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %, and the antiferromagnetic layer preferably comprises an alloy represented by the composition PtqMn100xe2x88x92qxe2x88x92jLj wherein L is at least one element of Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr, and the composition ratios q and j satisfy 48 atomic %xe2x89xa6q+jxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
A The composition ratios q and j of the antiferromagnetic layer more preferably satisfy 52 atomic %xe2x89xa6q+jxe2x89xa655.2 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %, or 56.5 atomic %xe2x89xa6q+jxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6jxe2x89xa610 atomic %.
6. The bias layers preferably comprise an alloy represented by the composition PtmMn100xe2x88x92mxe2x88x92nZn wherein Z is at least one element of Pd, Ir, Rh, Ru, and Os, and the composition ratios m and n satisfy 52 atomic %xe2x89xa6m+nxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %, and the antiferromagnetic layer preferably comprises an alloy represented by the composition PtmMn100xe2x88x92mxe2x88x92nZn wherein Z is at least one element of Pd, Ir, Rh, Ru, and Os, and the composition ratios m and n satisfy 48 atomic %xe2x89xa6m+nxe2x89xa658 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
The composition ratios.m and n of the antiferromagnetic layer preferably satisfy 52 atomic %xe2x89xa6m+nxe2x89xa655.2 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %, or 56.5 atomic %xe2x89xa6m+nxe2x89xa660 atomic %, and 0.2 atomic %xe2x89xa6nxe2x89xa640 atomic %.
The above problems can be solved by a method of manufacturing a spin-valve thin film magnetic element comprising the step of depositing in turn an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, a free magnetic layer, and a bias layer on a substrate to form a lamination, the step of heat-treating the lamination at a first heat treatment temperature while applying a first magnetic field in the direction perpendicular to the direction of the track width to produce an exchange anisotropic magnetic field in each of the antiferromagnetic layer and the bias layer so that the magnetization directions of the pinned magnetic layer and the free magnetic layer are pinned in the same direction, and the exchange anisotropic magnetic field of the antiferromagnetic layer is higher than that of the bias layer, the step of heat-treating the lamination at a second heat treatment temperature higher than the first heat treatment temperature while applying a second magnetic field higher than the exchange anisotropic magnetic field of the bias layer and lower than that of the antiferromagnetic layer in the direction of the track width to apply a bias magnetic field to the free magnetic layer in the direction perpendicular to the magnetization direction of the pinned magnetic layer, the step of removing a portion of the bias layer to form a concave having a width close to the track width and form a track groove having a width corresponding to the track width in a portion of the free magnetic layer located below the concave, and the step of forming a conductive layer on the bias layer, for supplying a sensing current.
In the method of manufacturing a spin-valve thin film magnetic element, each of the antiferromagnetic layer and the bias layer preferably comprises an alloy containing Mn and at least one element of Pt, Pd, Rh, Ru, Ir, Os, Au, Ag, Cr, Ni, Ne, Ar, Xe, and Kr.
In the method of manufacturing a spin-valve thin film magnetic element, the first heat treatment temperature is preferably in the range of 220xc2x0 C. to 240xc2x0 C.
In the method of manufacturing a spin-valve thin film magnetic element, the second heat treatment temperature is preferably in the range of 250xc2x0 C. to 270xc2x0 C.
FIG. 17 is a graph showing the relation between the heat treatment temperature of an antiferromagnetic layer and an exchange anisotropic magnetic field in each of a bottom type spin-valve thin film magnetic element and a top type spin-valve thin film magnetic element.
FIG. 17 indicates that in the bottom type spin-valve thin film magnetic element in which the antiferromagnetic layer is provided near a substrate (or the antiferromagnetic layer is provided below a pinned magnetic layer), the exchange anisotropic magnetic field of the antiferromagnetic layer (marked with ▪) is exhibited at 200xc2x0 C., and exceeds 600 (Oe) at near 240xc2x0 C. On the other hand, in the top type spin-valve thin film magnetic element in which the distance between the antiferromagnetic layer and the substrate is greater than the bottom type spin-valve thin film magnetic element (or the antiferromagnetic layer is provided above the pinned magnetic layer), the exchange anisotropic magnetic field of the antiferromagnetic layer (marked with ♦) is exhibited at 240xc2x0 C., and exceeds 600 (Oe) at about 260xc2x0 C. at last.
It is thus found that in the antiferromagnetic layer of the bottom type spin-valve thin film magnetic element in which the antiferromagnetic layer is provided near the substrate (or the antiferromagnetic layer is provided below the pinned magnetic layer), a high exchange anisotropic magnetic field can be obtained a relatively low heat treatment temperature, as compared with the top type spin-valve thin film magnetic element in which the distance between the antiferromagnetic layer and the substrate is greater than the bottom type spin-valve thin film magnetic element (or the antiferromagnetic layer is provided above the pinned magnetic layer).
The spin-valve thin film magnetic element of the present invention is the bottom type spin-valve thin film element in which the antiferromagnetic layer is provided near the substrate, and the bias layer made of the same material as the antiferromagnetic layer is provided at a larger distance from the substrate than the antiferromagnetic layer.
In the bottom type spin-valve thin film magnetic element in which the antiferromagnetic layer is provided near the substrate, the antiferromagnetic layer is provided below the pinned magnetic layer, while in the top type spin-valve thin film magnetic element in which the distance between the antiferromagnetic layer and the substrate is larger than the bottom type spin-valve thin film magnetic element, the antiferromagnetic layer is provided on the pinned magnetic layer.
Therefore, in the method of manufacturing the spin-valve thin film magnetic element of the present invention, for example, the lamination is heat-treated at the first heat treatment temperature (220 to 240xc2x0 C.) with the first magnetic field applied to produce an exchange anisotropic magnetic field in each of the antiferromagnetic layer and the bias layer so that the magnetization directions of the pinned magnetic layer and the free magnetic layer are pinned in the same direction. Furthermore, the exchange anisotropic magnetic field of the antiferromagnetic layer becomes 600 (Oe) or more, which is higher than the exchange anisotropic magnetic field of 100 (Oe) or less of the bias layer.
Next, the lamination is heat-treated at the second heat treatment temperature (250 to 270xc2x0 C.) with the second magnetic field applied perpendicularly to the first magnetic field so that the exchange anisotropic magnetic field of the bias layer becomes 600 (Oe) or more, which is higher than that of the bias layer produced in the first heat treatment. Therefore, the magnetization direction of the free magnetic layer crosses the direction of the first magnetic field.
At this time, the second magnetic field is set to be lower than the exchange anisotropic magnetic field of the antiferromagnetic layer, which is produced in the first heat treatment, so that even with the second magnetic field applied to the antiferromagnetic layer, the exchange anisotropic magnetic field of the antiferromagnetic layer does not deteriorate, and the magnetization direction of the pinned magnetic layer can be left pinned.
As a result, the magnetization directions of the pinned magnetic layer and the free magnetic layer can be crossed each other.
Therefore, in the method of manufacturing a spin-valve thin film magnetic element, an alloy having excellent heat resistance, such as a PtMn alloy, is used for not only the antiferromagnetic layer but also the bias layer, and thus an exchange anisotropic magnetic field can be applied to the bias layer in order to orient the magnetization direction of the free magnetic layer in the direction perpendicular to the magnetization direction of the pinned magnetic layer without adversely affecting the magnetization direction of the pinned magnetic layer. It is thus possible to orient the magnetization direction of the free magnetic layer in the direction perpendicular to the magnetization direction of the pinned magnetic layer, thereby providing a spin-valve thin film magnetic element having excellent heat resistance and symmetry of a reproduced signal waveform.
The method of manufacturing a spin-valve thin film magnetic element comprises depositing in turn the antiferromagnetic layer, the pinned magnetic layer, the nonmagnetic conductive layer, the free magnetic layer and the bias layer on the substrate to form the lamination, and then heat-treating the lamination. Therefore, in forming the lamination, the surface of each of the layers formed between the substrate and the bias layer is not exposed to air, and thus need not be cleaned by ion milling or reverse sputtering apart from cases in which the surface of each layer is exposed to air and is thus cleaned before forming upper layers. The manufacturing method is thus simplified and exhibits good reproducibility. Since the surface of each of the layers need not be cleaned by ion milling or reverse sputtering, the manufacturing method causes no problem resulting from cleaning, such as contamination with matters adhering to the surfaces, the adverse effect of the disordered surface crystal state on the occurrence of an exchange anisotropic magnetic field, etc.
The method of manufacturing a spin-valve thin film magnetic element comprises removing a portion of the bias layer to form a concave having a width near the track width and form a track groove having a width corresponding to the track width in a portion of the free magnetic layer, which is located below the concave. Therefore, even with variation in the thickness of the bias layer, the bias layer does not remain at the bottom of the track groove, thereby precisely defining the track width, and obtaining a spin-valve thin film magnetic element adaptable to hither recording density. Since a portion of the bias layer can be easily completely removed, a thin film magnetic element can easily be manufactured.
A thin film magnetic head of the present invention comprises the above-described spin-valve thin film magnetic element provided on a slider.
The thin film magnetic head exhibits excellent durability and heat resistance, and produces a sufficient exchange anisotropic magnetic field.